1. Field of the Invention
This invention relates to a pneumatically driven power tool, more particularly to an air cylinder apparatus for a pneumatically driven power tool, which has a unitary outer cylinder member that can be manufactured easily and conveniently.
2. Description of the Related Art
Referring to FIG. 1, a conventional air cylinder apparatus 1 for a pneumatically driven power tool is shown to include a cylindrical wall 11, a front bearing member 12 and a rear bearing member 13. A rotor 10 is disposed within a cylindrical chamber 111 that is formed eccentrically within the cylinder wall 11, and is journalled on the front and rear bearing members 12, 13. The cylindrical wall 11 has forward and reverse guideways 112, and two exhaust ports 113. Each of the front and rear bearing members 12, 13 is provided with a bearing 15. The rotor 20 has a rotating shaft, which extends through bearing holes 121, 131 in the front and rear bearing members 12, 13. The rear bearing member 13 has two aligned semi-circular slots 132 that extend around the bearing hole 131, and two air ports 133, which guide air into the chamber 111 for rotating the rotor 10. The front bearing member 12 has two aligned semi-circular slots (not shown) that are formed in an inner side surface thereof. Because the cylindrical wall 11 is bored by a lathe to form the chamber 111, it is time-consuming to manufacture the apparatus 1, thereby increasing the manufacturing costs.